The issue of light extraction from light-emitting diodes (LEDs) is well-known. LEDs are made of a high refractive index semiconductor material. Unfortunately, a fraction of the light generated by the LED internally reflects from the interfaces with the outside medium (either air or an encapsulant) due to total internal reflection. This light is called guided light. Its existence is detrimental to the performance of the LED because it limits light extraction. Various approaches can be used to extract guided light, such as shaping the LED, or roughening some of the surfaces. These approaches aim at breaking the guided trajectories so as to increase light extraction. However, conventional techniques fail to reduce the guided light and thereby fail to maximize light extraction from LEDs.
Therefore, improved methods for increasing light extraction efficiency and in particular reducing guided light in LEDs is desired.